1. Field of the Invention
The present invention relates to image processing apparatuses, image processing methods, and printer drivers. More particularly, the present invention relates to an image processing apparatus and an image processing method for carrying out processing for converting input image data into data for inks of a plurality of colors. Furthermore, the present invention relates to a printer driver and a recording apparatus for executing the above-described image processing method.
2. Description of the Related Art
A color ink-jet printer, as one example of color output apparatuses, is widely used due to its advantage that it supports various types of output media including paper and film. Many color printers use recording agents (inks) of three colors: cyan (C), magenta (M), and yellow (Y) or four colors: C, M, Y, and black (K) for image formation. In a typical printer, image data to be recorded is converted into data for recording agent that realizes the colors supported in the printer according to predetermined color processing parameters before it is recorded.
In ink-jet recording apparatuses, which use water-based ink, recording media such as paper often fail to absorb water completely, leading to problems such as mixture of different inks, paper cockling that cause interference between the recording apparatus and the recording element. To avoid such problems, the amount of ink delivered per unit area is restricted in accordance with the recording medium and the recording method employed. Hereinafter, this amount of ink is referred to as “the amount of shot-in ink”.
The amount of shot-in ink is affected by two factors: one is related to the recording medium itself and depends on the type of recording medium and the thickness of the ink-absorbing layer, and the other depends on the recording speed and method. In general, as the recording speed increases, the absorbed amount of ink decreases. Furthermore, the amount of shot-in ink should be restricted in recording modes in which paper cockling should be suppressed to a lower level by the method from paper feeding to paper ejection. In recording modes for recording on both sides of one sheet of paper, a recording method for decreasing the density over the entire area may be employed in order to prevent low visibility of images due to ink bleeding through the paper. Furthermore, the amount of shot-in ink is also decreased in recording modes intended to reduce the amount of ink for the purpose of reducing the running cost. As described above, the desired amount of shot-in ink differs depending on the recording medium, the recording method, and the purpose.
One technique for realizing recording media and recording methods that support different amounts of shot-in ink is to decrease the amount of shot-in ink by thinning recording with respect to a recording mode in which the amount of shot-in ink is large. For this thinning recording, the colors may be uniformly thinned or the amount of thinning may differ for each color.
A known method performs control such that the amount of shot-in black ink differs from those of shot-in color inks depending on the recording medium and the recording mode, thus preventing problems appearing on recorded images.
U.S. Pat. No. 5,661,508 (Patent Publication No. 02952077) discloses a recording apparatus for ejecting a plurality of inks while moving a plurality of recording heads relative to the recording medium for recording. Furthermore, there is disclosed a method that, when a thinned image is to be recorded on this recording apparatus, changes the amount of ink to be delivered to the recording medium for each color by causing the thinning rates corresponding to respective recording heads to differ from one another.
Japanese Patent Laid-Open No. 2000-355158 describes a structure in which the amount of ink to be delivered to the recording medium is different depending on the ink color. More specifically, the maximum amount of shot-in black ink onto the recording medium is controlled to become smaller than those of shot-in color inks.
It is not only for ink-jet recording apparatuses that the amount of delivered color material is restricted as described above. For example, the amount of color material is also controlled with electrophotographic methods and thermal transfer methods that use resin-based toner in order to maintain the glossiness and image fastness. In addition, it is known that the running cost can be reduced by restricting the amount of color material to be delivered. Therefore, a reduction in the amount of color material to be used is also conceivable to reduce the running cost.
However, since the known technique uniformly thins the amounts of shot-in inks regardless of the gray level, although superior gradation performance is maintained, excessive thinning is carried out even in areas with a sufficient margin for the amount of shot-in ink to decrease the density. In particular, high density is preferred for black because thick characters are highly recognizable and superior gradation performance and contrast are maintained. For this reason, excessive thinning is not desired for black.